Method of sintering clay



Dec. 30, 1930. J] E REENAWALT. 1,786,714

METHOD OF SINTERING CLAY Filed Feb. 16, 1929 hvwavraa; JOHM f. GREEN/4WA L I Hrroe/m'r UNITED STATES PATENT OFFICE JOHN E. GBEENAWALT, on NEWYORK, N. Y.

METHOD OI SINTERING CLAY Application filed February 16, 1929. sem No.340,643.

My invention relates to an. improved process of sintering argillaceousmaterial to produce an artificial concrete or mortar material in placeof crushed stone, gravel and sand.

' Heretofore, clay, slate, shale and other argillaceous materials havebeen calcined in kilns or furnaces heated in the usual manner to producea light weight aggregate. It has also been proposed to heat treat afinely crushed charge of mixed clay and fuel on a sintering apparatus inthe same manner that ores are sintered.

However, owing to the plasticity of the clay and the tendency of theparticles to adhere, 5 the free passage of air through the charge isobstructed, rendering it impossible to maintain, the sintering actionthroughout the charge, unless special precautions are taken to preservethe voids in the charge. I have found that these voids, so essential toeither downdraft or updraft sintering, may be preserved by treatmg thematerial with a view {:0 improving its physical condition as folows:

The clay, or similar material, is first crushed by any suitable deviceto a fineness, that on mixing the material with water will produce aslurry. I' do not wish to be restricted to a process in which the wateris added to the material after the same is crushed, as my invention maybe practised with equal facilit by adding the water either before orduring the crushin operation. The slurry is then subjected to ead whilebeing mechanically a 'tated so that it will dry in the condition 0 smallbodies approximately the size of a pea. These small bodies may then bestored (if desired) until it is convenient to charge them into asintering appara- 40 tus. This drying operation need not be continueduntil all moisture is expelled, but merely to the point where the ballswill not stick to ether. 1 V

n treating some clays '-1t may notbe necessary to produce a slurry, butthe formation of the small bodies, or balls, may be effected by forcingthe clay, in the. condition of soft mud throu h a suitablescreening'device. However, t e balls should be dried, pref- V so, erablyby the application of 'heat beforethey' are stored. If the sintering ofthe clay is to be eifected immediately as a part of a continuousoperation, the moist balls ma be dusted with pulverized fuel, which willorm a coating about them. The fuel coated clay balls, in a moistcondition, may now be charged into a sintering pan and the sinteringoperation performed in the usual way; that is, by passing a blast of airthrough the charge and igniting the fuel constituent thereof at itssurface.

In the drawing-I show a Greenawalt apparatus, comprismg asintering pan 1and connected through its'hollow trunnions 2, 2 and conduits 4, 4 to adust chamber 3, through which air is drawn by means of an exhauster 5,having its outlet 6 connected to a stack 7. The usual charge car 8 isprovided for feeding the material constituting the charge onto the grate9 of the sintering pan 1, after which the igniter 10 is brought intoposition over the charge for the purpose of effecting ignition at itssurface. After ignition of the charge the igniter is either removed orthe flame extinguished as combustion is continued internally of thecharge under the influence of the air blast. The small bodies, or balls,that are formed by the above described operation obviously will not beof a uniform size and they may be separated, if desired, so into two ormore components m and m; the larger balls m being fed directly onto thegrate 9, and the smaller balls m being charged on top of the'largerones. However, the manner of .arrangingthe charge is optional with theoperator who will perform the operation as experience teaches him, withthe view of obtaining the most satisfactory results.

The physical condition of the charge, made up as it is of a mass ofsmall bodies, insures the presence of voids throughout, so that the airmay pass freel through it to sustain combustion of the uel. As thecombustion of the fuel propagates itself throu h the charge, the smallclay bodies are su jected to intense heat and are burnt hard. The escapeof occluded gases in the bodies is readily accomplished because of theirsmall mass, so that'the burnt clay bodies become highly porous. At thesame time fusion occurs at the surfaces of the bodies causing them to becemented together into a hard, lightweight porous mass of clay sinter.This mass or cake of clay sinter may then be pressed to any sizerequired by the ultimate use that is to be made of it. In makingconcrete blocks, both the finely and the coarsely crushed particles ofsinter are mixed with the desired amount of Portland cement and water,and molded to shape. If the clay sinter is to be used merely as a mortarmaterial it may be mixed with cement or lime in any proportion selectedby the builder, according to his purpose.

In sintering some clays it may be desirable to mix powdered fuel withthe clay before it is balled. Then again certain conditions may requirethat the clay balls and the fuel be independently charged into theslntering pan in such a manner that the voids between the balls befilled with fuel. In fact, I do not wish to be restricted in any respectas concerns the fuel, as the essence of this invention is the treatmentof the clay to produce small bodies, or balls, which are massed in aholder to constitute a charge to be sintered.

The invention may be modified to the extent that only suflEicient claybe used in the charge to render it plastic. The balance of the charge(aside from the fuel) may be nonplastic argillaceous matter, such asslate or shale, or even other substances such as ashes, crushed brick,or any mixture of substances provided plastic clay is present insuflicient amount to render the mixture susceptible to the ballingoperation. From 10% to 15% of plastic clay is sufficient fonthispurpose.

Aside. from the excellence of the sintered clay product, there are twoother very important advantages in sintering argillaceous material. Oneof them is the speed of the operation (but a few minutes being requiredto sinter a charge weighing several tons), and the other is the economyof the use of the fuel, the amount of which can be quite accuratelydetermined for the best results. With combustion taking place within thecharge very little heat is wasted.

Having described my invention, I claim:

1. The process of manufacturing an aggregate for mortars or concretes,which comprises reducing argillaceous material to a finely dividedcondition, adding water thereto to form an agglutinated mixture,converting said mixture into a homogeneous mass of small bodies, andarranging said bodies on a permeable hearth to form a charge, effectinga distribution of fuel throughout said charge, igniting the fuel at onesurface of the charge,

causin asupporter of combustion to pass throng the charge away from saidignited surface, whereupon combustion of the fuel will proceed throughthe charge and produce a hard, porous, burnt product.

2. The process of manufacturing an aggregate for mortars or concretes,which comprises reclucing argillaceous material to a finely dividedstate, adding water to the finely divided material to form a slurry,subjecting the slurry to mechanical action and heat to form smallbodies, arranging a mass of said bodies and finely divided fuel on asuitable support to constitute a charge, maintaining the particles ofthe charge in a quiescent condition and subjecting said mass to heat anda blast of air to form a hard, porous product.

3. The process of manufacturing an aggregate for mortars and concretes,which comprises reducing argillaceous material to a finely dividedcondition, mixing finely divided fuel therewith, adding water to saidmixture to agglutinate the same, converting said mixture into ahomogeneous mass of small bodies, arranging said bodies in a layer,igniting the exposed surface of said layer, passing air through thelayer away from said surface to cause combustion of the fuel throughoutthe layer to form a hard porous product.

4. The process of manufacturing an aggregate for mortars or concretes,which comprises reducing argillaceous material to a finely dividedcondition, converting said mixture into a homogeneous mass of smallbodies, and arranging said bodies on a permeable hearth to form acharge, effecting a distribution of fuel throughout said charge,igniting the fuel at one surface of the charge, causing a supporter ofcombustion to pass through the charge away from said ignited surface,whereupon combustion of the fuel will proceed through the charge andconvert the same into a hard, porous product.

5. The process of manufacturing an aggregate for mortars or concreteswhich comprises reducing argillaceous material to a homogeneous mass ofsmall bodies, arranging said bodies on a permeable hearth to form acharge, subjecting said charge to heat and simultaneously therewithcausing a sup orter of combustion to pass through said 0 arge, whereuponthe said bodies become fused and agglomerated to form a hard, porouscake.

6. The process of manufacturing an aggregate for mortars or concreteswhich comprises mixing finely divided ar illaceous material with fuel,converting sai mixture into an ag lutinated mass, forming a multitude ofsmall odies from said mass, arranging said bodies in a layer to form acharge, igniting said charge at one'surface and causing a supporter ofcombustion to traverse the charge to propagate combustion throughout themass to form a hard,porous, agglomerated product.

7 The process of manufacturing an aggreate for mortars or concreteswhich comprises orming a multitude of small bodies from finely dividedargillaeeous material, arrangingamixture ofsaidsmallbodies and fuel in alayer to form a charge, igniting the charge at its exposed surface,passing air through the charge away from the ignited surface topropagate combustion throughout the charge and produce a hard, porousagglomerated product.

In testimony whereof I hereunto afiix my signature.

- JOHN E. GREENAWALT.

